Re: [PATCH RFC 2/3] dmaengine: dma-axi-dmac: Switch to bitmap-based address width masks

["Nuno Sá" <noname.nuno@gmail.com>]

On Tue, Jun 16, 2026 at 11:23:39AM -0500, Frank Li wrote:
> On Tue, Jun 16, 2026 at 04:40:53PM +0100, Nuno Sá via B4 Relay wrote:
> > [You don't often get email from devnull+nuno.sa.analog.com@kernel.org. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> >
> > From: Nuno Sá <nuno.sa@analog.com>
> >
> > Advertise the source and destination bus widths through the new
> > dma_set_{src,dst}_addr_mask() helpers instead of open-coding the legacy
> > BIT() mask. This moves the driver onto the representation that can
> > express widths of 32 bytes and above and allows the legacy u32 field to
> > be removed once all users are converted.
> >
> > While at it, give the channel width members their proper
> > enum dma_slave_buswidth type.
> >
> > Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> > ---
> >  drivers/dma/dma-axi-dmac.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
> > index d47ff27e1408..19c258d511ca 100644
> > --- a/drivers/dma/dma-axi-dmac.c
> > +++ b/drivers/dma/dma-axi-dmac.c
> > @@ -152,8 +152,8 @@ struct axi_dmac_chan {
> >         struct list_head active_descs;
> >         enum dma_transfer_direction direction;
> >
> > -       unsigned int src_width;
> > -       unsigned int dest_width;
> > +       enum dma_slave_buswidth src_width;
> > +       enum dma_slave_buswidth dest_width;
> >         unsigned int src_type;
> >         unsigned int dest_type;
> >
> > @@ -1262,8 +1262,12 @@ static int axi_dmac_probe(struct platform_device *pdev)
> >         dma_dev->device_terminate_all = axi_dmac_terminate_all;
> >         dma_dev->device_synchronize = axi_dmac_synchronize;
> >         dma_dev->dev = &pdev->dev;
> > -       dma_dev->src_addr_widths = BIT(dmac->chan.src_width);
> > -       dma_dev->dst_addr_widths = BIT(dmac->chan.dest_width);
> > +       ret = dma_set_src_addr_mask(dma_dev, &dmac->chan.src_width, 1);
> > +       if (ret)
> > +               return ret;
> > +       ret = dma_set_dst_addr_mask(dma_dev, &dmac->chan.dest_width, 1);
> > +       if (ret)
> > +               return ret;
> 
> 
> This patch is okay.  I think most system only set one width once, do we
> really need pass down arrary.

I think so. See:

https://elixir.bootlin.com/linux/v7.1/source/drivers/dma/st_fdma.c#L723
https://elixir.bootlin.com/linux/v7.1/source/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c#L1565
https://elixir.bootlin.com/linux/v7.1/source/drivers/dma/hsu/hsu.c#L475

And likely there are more. To fully support all widths I'm not seeing
any other obvious way.

- Nuno Sá
> 
> Frank
> 
> >         dma_dev->directions = BIT(dmac->chan.direction);
> >         dma_dev->residue_granularity = DMA_RESIDUE_GRANULARITY_DESCRIPTOR;
> >         dma_dev->max_sg_burst = 31; /* 31 SGs maximum in one burst */
> >
> > --
> > 2.54.0
> >
> >